WLCSP Testing & Bumping Process - Faraday-tech.com

A WLCSP die has a first layer of organic dielectric (Polyimide 1), a metal redistribution layer (RDL) to re-route the signal path from the die peripheral I/O to ... WaferLevelChipScalePackagereferstothetechnologyofpackaginganintegratedcircuitatthewaferlevel,insteadofthetraditionalprocessofassemblingindividualunitsinpackagesafterdicingthemfromawafer.ThisprocessisbasicallyanextensionofthewaferFabprocesses,wherethedeviceinterconnectsandprotectionareaccomplishedusingthetraditionalfabprocessesandtools.Inthefinalform,thedeviceisessentiallyadiewithanarraypatternofbumpsorsolderballsattachedatanI/Opitchthatiscompatiblewithtraditionalcircuitboardassemblyprocesses.WLCSPisessentiallyatruechip-scalepackaging(CSP)technology. WLCSPtechnologydiffersfromotherball-gridarray(BGA)andlaminate-basedCSPsinthatnobondwiresorinterposerconnectionsarerequired.ThekeyadvantagesoftheWLCSPisthedietoPCBinductanceisminimized,reducedpackagesize,andenhancedthermalconductioncharacteristics. WLCSPTurnkeyServiceFlow   WLCSPConstruction RefertothefigurebelowforarepresentationofatypicalWLCSPpackagewithRedistributionLayer(RDL)andUnderBumpMetallization(UBM)process.AWLCSPdiehasafirstlayeroforganicdielectric(Polyimide1),ametalredistributionlayer(RDL)tore-routethesignalpathfromthedieperipheralI/Otoanewdesiredlocation,andasecondpolyimidelayer(Polyimide2)tocovertheRDLmetal,whichinturnispatternedintothesolderballarray.Topreventdiffusionandenablesolderwetting,anunder-bumpmetallization(UBM)layerisdepositedontheRDL.Thesolderballisalead-freealloy.Backsidewaferlamination,aprotectivepolymerfilm,isoptionalforWLCSPproductions.Thispolymermaterialoffersbothmechanicalcontact(i.e.SMTassemblypickandplace)andUVlightprotectiontothebacksideofthediesurface.